594 MESSES. E. HERON-ALLEN AND A. EAELAND ON THE 



Diameter in all directions : circa 'IS mm., diameter of tube in final convolution 

 •02 mm. 



This curious little form is chiefly interesting on account of its isomorphism with 

 AmmoclisG'us charoides (Jones & Parker). 



Peneeoplis Montfort. 



Introductory Note. — As is usually the case in a series of gatherings from such 

 shallow waters in tropical seas, the genus Peneroplis figures prominently in the 

 Kerimba Archipelago material and presents practically all the variations hitherto 

 recorded and separated in the costate group, the smooth and polished forms alone 

 being absent. Regard being had to the large size attained by many of the specimens, 

 notably among those of the type of P. planatus, the shell-development observed in the 

 dredgings is rather poor, the individuals found being nearly all translucent and thin- 

 walled, though otherwise well-grown and characteristic. As might be expected in 

 such a mass of material, abnormal and deformed specimens (especially of the 

 P. "planatus and P. pertusus types), in which the plane of growth frequently changes, 

 and in which the growth becomes wild (as shown in d'Orbigny's " Planche inedite " and, 

 more elaborately, in Dreyer's work upon the genus *), are of frequent occurrence. A 

 case of fusion was observed at Stn. 10, where two individuals of P. carinatus were 

 found associated, their initial chambers being at opposite poles of the combined mass. 

 Instances of the Spaltungsmonstra figured and described by Rhumblerf, however, 

 were not found. 



In attempting to discriminate between specimens of the elongate, terminally 

 uncoiled, or " Spirolina " group, the Ehizopodist is at once confronted with an almost 

 insuperable difficulty in identifying the types referred to by the early authors, upon 

 Avhose confusing figures and very insufficient diagnoses subsequent writers have 

 attempted to separate such species as P. arietinus, P. cylindraceus, and P. lituus. It 

 may be observed that the available material has been very efficiently marshalled and 

 discussed by Dreyer in the work above referred to *, and his plates are of 

 exceptional completeness and excellence. 



This difficulty has been increased by Brady, who, in his analysis of the genus, has 

 definitely separated the figure 15 c (text-fig. 42, A), Nautilus arietinus, in Batsch's 

 extremely rare work J, as the type of P. arietinus, whilst relegating his three figures, 



* F. Drej'er, ^Peneroplis -. eine Studie zur biologiachea Morphologie mid zur Speoiesfrage ' (Leipzig, 189S). 



t R. 1909, etc., EPE. 1909, p. 193, pi. xii. fig. 13. 



X B. 1791, CS. Of this work there exists a perfect copy of the German Edition in the Library of the 

 Eoyal Society. The copy in the Eritisli Museum (Bloomsbury) lacks the coveis and the descriptive letter- 

 press. Of the Latin Edition ' Testaceorum Arenulse Mariuse, Tabulae sex priores ' (Jena, 1791), referred to 

 in C. Lavies Sherborn's ' Bibliography of the Foraminifera ' (London, 1888, see p. 9), apparently the only 

 two copies in existence are in our own library (see J. E. M. S. 1914, p. 596). 



